# Problem with TLorentzVector boost

hello everybody,

I am trying to boost a TLorentzVector but something goes wrong.

Here is an example:

[code]TLorentzVector LV;
TVector3 v;
LV.SetXYZT(1.,1.,1.,10.);
v.SetXYZ(1,2,3);

LV.Print();

LV.Boost(v);

LV.Print();[/code]

The output is:

quote=(1.000000,1.000000,1.000000,10.000000) (P,eta,phi,E)=(1.732051,0.658479,0.785398,10.000000)
Warning in TVector3::PseudoRapidity: transvers momentum = 0! return +/- 10e10
(x,y,z,t)=(-nan,-nan,-nan,-nan) (P,eta,phi,E)=(-nan,-100000000000.000000,-nan,-nan)[/quote]

Why? Can anybody help?

Hi,

the boost vector should be expressed in terms of Beta_x, Beta_y and Beta_z i.e. three numbers smaller than one. We’ll make it clearer in the documentation!

Cheers,
D

Another thing regarding your initial post.
The warning was already noticed (sft.its.cern.ch/jira/browse/ROOT-7900) and has been fixed in ROOT starting from release 6.08.

Cheers,
Danilo

thanks!!